Brazing, soldering, or the like process



Nov. 19, 1946. G. H. LEE

.BRAZING, SQLDERING, OR THE LIKE PROCESS Filed June 9, 1944 In HimPatented Nov. 19, 1946 BRAZING, SOLDERING, OR. THE LIKE PROCESS GeorgeHerbert Lee, Bristol, England, assignor to The Bristol Aeroplane CompanyLimited, Bristol, England, a British company Application June 9, 1944,Serial No. 539,577 In Great Britain April 6, 1943 1 Claim.

This invention concerns improvements in or relating to brazing,soldering or the like processes.

According to the present invention a brazing, soldering or the likeprocess is characterised in that the parts to be united by the processare rtated together whilst the brazing, soldering, or the like materialis in a molten condition whereby said material is caused to now oversaid parts by centrifugal action.

According to another feature of the present invention the process ischaracterised in that the parts to be united by the process are rotatedtogether at a varying speed whilst the brazing, soldering or the likematerial is in a molten condition whereby said material is caused to ebband flow over said parts.

The invention has particular application to the production of the baseof a junk-head of a sleevevalve internal combustion engine. Accordinglyin order that the invention may be clearly understood, the production ofsuch a junk-head will now be described, merely by way of example, withreference to the accompanying drawing whereon:

Figure 1 is a side elevation of a junk-head which has been produced by aprocess in accordance with the invention, the head being shown partly insection, and

Figure 2 is a perspective view of an apparatus for carrying out saidprocess.

Referring to Figure 1, the junk-head H) is of two-piece construction-onepart thereof is a base I l and the other part is a steel sleeve l2 towhich the base I! is attached and which is itself secured to thecylinder by studs passing through the fiange I3.

The base [I comprises a plate l4, one face 15 of which is dish-shapedwith a generally fiat central portion [6, and a plurality of fins l'lsecured by brazing to the .face l5 and the inner surface of sleeve [2.The fins ll are approximately of a corresponding configuration to theface to which they are attached.

The fins, which are pre-iormed, are made to be a loose fit with theinclined wall of face I5 and the brazed joint is of such a depth thatcomplete contact between the lower edge of the fin and the inclined wallis ensured. Whilst the fins can be readily machined to be in moreintimate contact with the fiat central portion than with the inclinedwall it is desirable that this brazed joint should also be of aconsiderable depth to ensure complete contact. By providing this form ofbrazed joint it is unnecessary to ma chine the fins with special care toprovide for their varying edge shape as would be required if intimatecontact between the fins l! and the face l5 was required: thissimplifies the production of the fins and their assembly on the base.

The upper edges of the fins H are secured to a tray is which liestransversely of the fins. The tray has a central opening l9 to permitspark plugs to be passed down into the head and screwed into thespark-plug adaptors 29 which are carried in the plate Hi. The adaptorsare screwed into the plate and then brazed in. The fins ll extendparallel to each other and chordwise across the sleeve. To enable thespark plugs to pass downwardly to the adaptors 2E], those fins whichwould otherwise extend across the sparkplug holes are terminated at theedge thereof. There is thus formed a tunnel through which the plugs passwhen being fitted to the head.

The base i i is received by the steel sleeve l2, a spigot joint beingprovided by extending the inclined wall of the face i5 upwardly withinthe sleeve. The base i l is brazed to the sleeve at the spigot joint 2|.

The fins ll are brazed to the face Hi, the adaptors Zll into the base H,and the latter to the sleeve l2 by a single brazing operation. Inpreparation for this operation the following treatments are carried outon the separate parts:

1. The adaptors 2% are coated with a flux and are then screwed into theplate M. The face l5 of the base is brushed with a solution of the fluxin water and finally a similar treatment is applied to the face of thespigot joint 2| for the base.

2. The steel sleeve 22 is coated with a brazing material by dipping thesleeve into a bath, the outside surface being protected by a heatresistant cement. To ensure adhesion of the brazing material, the insideand lower edge of the sleeve ii. is brushed with flux. The sleeve isdipped in the bath of molten brazing material to a depth greater thanthe height of the fins on assembly.

When the sleeve has attained the temperature of the bath and the coatingis complete it is removed and allowed to cool. The excess brazingmaterial is removed from the sleeve so that finally a thin continuouscoat is left on the inner surface and lower edge of the sleeve.

3. The edges of the fins H (which fins are attached to the tray !8 so asto form a pack) are not previously coated with flux in preparation forthe brazing operation.

The base plate M, sleeve 52, and the pack of fins are then assembled.The pack of fins is first placed upon the face I of the plate l4(ensuring that the fins are properly positioned relative to the plugadaptors) and then the steel sleeve I2 is spigoted on to the plate I 4.A retaining band 42 is then placed in position on the outer cylindricalsurface of the head so that it encircles the plate l4 and sleeve l2 tothe same height as the fins H. The purpose of this band is to seal thespigot joint 2| so that during brazing the molten brazing material isunable to leak through the joint under the centrifugal force to which itis subjected.

The various parts having been treated and assembled as described above,the brazing operation is now performed.

The apparatus which is provided for this purpose is shown in Figure 2and comprises base [plate 22, a pedestal bearing 23 carried by the baseplate, a rotatable platform 24 supported from the bearing 23 by theshaft 25, a pulley 26 which is suitably driven by a belt 27 so as torotate the platform 24, a gas burner 28 disposed below the platform 24and supported upon legs 29, and a cylindrical shield 30 which rests uponthe legs 29 and envelops the gas burner, the platform and the headassembly. Gas passes to the burner 23 by a pipe 3|. The pulley 26 isdriven from an electric motor (not shown) by belt 21, the arrangementbeing that the speed of said motor is variable to vary the speed ofrotation of the platform 24.

The head assembly in preparation for the brazing operation is mounted onplatform 24 and clamped in position thereon. The clamping means providedis shown in Figure 2 and comprises a spider 32 which extends across theflange-end of the sleeve |2, arms 33 which engage the spider 32 and thelugs 34 of the platform support 35, and bolts 36 which are capable ofengaging the flange I3 of sleeve I2. When the bolts 3-3 are tighteneddown the clamping means described serves a dual function of clamping thehead assembly to the platform 2'4 and of forcing the sleeve l2 intointimate contact with plate M at the spigot joint 2|.

1 It is also necessary to press the pack of fins into contact with theface l5 of the plate I4 and to prevent relative movement between saidpack and the plate during rotation of the platform 24. To this end aturn-bolt 31, which is threaded in the boss of the spider 32, engages astirrup 38 whose ends rest upon a ring 3!? that lies upon the upper edgeof the pack of fins. When the bolt 37 is screwed downwardly upon thestirrup 38 the latter forces the ring 39 against the pack of finsthereby clamping the latter in proper relationship upon the plate Hi.

The head assembly having been clamped in position on the platform 24 asdescribed a quantity of the flux dissolved in water is poured into thehead assembly. The gas burner 28 is lit, the shield 35 placed inposition so that hot material within the head assembly is incapable ofbeing thrown out against the operator, and the electric motor is startedup. During the heating of the head assembly the speed of rotation of theplatform 24 is varied continuously in order to cause the flux to washover all the surfaces of the parts to be brazed.

The heat of the ring 28 is adjusted so that the time required for thehead to reach the brazing temperature (approximately 730 C.) is aboutten minutes.

, Whilst the head assembly is being heated up as indicated, a quantityof the brazing material is melted in an iron pot 40 which, as shown inFigure 2, is provided with a spout for pouring the molten material fromthe bottom of the pot. When the head has reached the required tem- 5perature (which is indicated to the operator by the melting of a smallstrip of the brazing material lying upon the portion N5 of the face IS)the platform 24 is brought to rest and the contents of the pct 40 arepoured into the head assembly. The molten brazing material is poured onto the plug adaptors 2|) and over the joints between the tray |8 and thefins When the contents of the pot 40 have been introduced to. the headassembly the electric motor is startedand during the subsequent twominutes the assembly is twice speeded up from rest to the maximum speedof 350 R. P. M.at which the molten brazing material reaches the top ofthe fins.

When the second speeding up of the platform 24 has been accomplished thespeed of the platform is reduced to 150 R. P. M. and the burner 28 isextinguished. The speed is maintained until the temperature of the headassembly has fallen well below the melting point of the brazingmaterial. The head is then slowly cooled in air.

In order to clean the inside of the head and to remove excess fiux thewhole of the inside surface of the sleeve l2, face l5 and the fins H areWashed with dilute nitric acid and then with water to remove the acid.

In order to relieve any stresses introduced into the head during coolingfrom the brazing tem-- perature the finished head is subjected to a heattreatment at 450 C. for one hour.

It will have been understood from the above description of the brazingoperation that the adaptors 2d are secured to the plate I4, that thesleeve L2 and plate M are united at the spigot joint 2| and that thefins I"! are attached to the faces l5, l5 and the inner surface of thesleeve l2 in a single brazing operation. By varying the speed ofrotation of the platform 24 whilst the brazing material is in a moltencondition'the brazing material is made to flow over the surfaces l5,I'E. Moreover, by selecting a suitable speed of rotation for theplatform 24 whilst the brazing material is solidifying, a predetermineddepth of brazing material is provided over the 50 surfaces is and H5.The depth of this layer of material is such that complete contact isensured between the fins l? and face |5.

It will be noted from Figure 1 that the rings which are commonlyprovided to form a seal between the head ill and the sleeve-valve areadapted to be carried by a member 4|. This ring carrier, which is ofcast iron, is provided because of the poor Wearing qualities which thebase plate l4 possesses When this is produced from copper or a copperalloy.

The carrier 4| may be shrunk upon the plate E4 or alternatively shrunkand brazed thereon.

When it is proposed to shrink and braze the carrier 4| to the plate l4,a number of holes 43 05 are drilled from the inclined portion of face IEto the stepped portion thereof which receives the carrier 4|, theseholes being placed around the periphery of the plate I4. The cast ironcarrier is dipped in a bath of molten brazing ma- 7 terial so that thelatter coats the surface thereof which will engage with the plate l4.The other surfaces are protected from the molten material by a coatingof heat resistant cement. The coated carrier 4| is slowly cooled in airand then 76 the excess brazing material is removed'so that its diametraldimension will provide an interference with the plate M. The carrier 41is then Washed with flux, heated and shrunk on to the plate 24. The headassembly with the carrier H is then mounted upon the platform 24 and thebrazing operation described above performed. The retaining band 42previously referred to is provided to cover the joint between thecarrier ti and the plate hi and the spigot joint 2! se that the moltenbrazing material is to escape through these two joints.

It is to be understood that although in the embodiment described theparts to be brazed together are rotated about a vertical axis, this maycertain cases be done about a horizontal or other axis dependent uponthe construction of the parts to be joined.

I claim:

A brazin process for simultaneously uniting 6 a plurality of coolingfins to the bas of a junkhead or" a sleeve-valve internal combustionengine and the base to a tubular Wall of the head comprising assemblingthe fins to the base and the base to the Wall, introducing a flux to theassembled head, heating the assembled head and simultaneously rotatingit to Wash the adjoining e head, rotating the latter a varying speed lstcontinuing to heat the head to cause the :n material to flow over thejunction of the and the base and of the base and the wall, head, andcontrolling the speed of rotation during the cooling step to determinethe form of the brazing joint between the fins and the and between thebase and the tubular Wall.

and the walh introducing a. brazing material to GEORGE HERBERT LEE.

